1 / 56

Fermi-LAT Study of Cosmic-rays/Diffuse Gamma-rays and Implications on Particle Physics

Fermi-LAT Study of Cosmic-rays/Diffuse Gamma-rays and Implications on Particle Physics. Mar. 7, 2011 @ Kyoto Univ. Tsunefumi Mizuno (Hiroshima Univ.) On behalf of the Fermi-LAT collaboration. Fermi 衛星による広がったガンマ線・ 宇宙線電子の観測と基礎物理への制限. 2011 年 3 月 7 日 @ 京都大学基礎物理研究所 水野　恒史 ( 広島大学理学部 )

miette
Download Presentation

Fermi-LAT Study of Cosmic-rays/Diffuse Gamma-rays and Implications on Particle Physics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Fermi-LAT Study of Cosmic-rays/Diffuse Gamma-rays and Implications on Particle Physics Mar. 7, 2011 @ Kyoto Univ. Tsunefumi Mizuno (Hiroshima Univ.) On behalf of the Fermi-LAT collaboration

  2. Fermi衛星による広がったガンマ線・宇宙線電子の観測と基礎物理への制限Fermi衛星による広がったガンマ線・宇宙線電子の観測と基礎物理への制限 2011年3月7日 @ 京都大学基礎物理研究所 水野　恒史 (広島大学理学部) On behalf of the Fermi-LAT collaboration

  3. Introduction Fermi LAT instrumentation Galactic Diffuse Gamma-rays Behind the diffuse gs: EGB and DM search Cosmic-ray Electrons Outline

  4. Gamma-ray Sky • GeV gamma-ray sky = Point sources + Diffuse Gamma-rays >=80% of g-rays Geminga Vela Crab 3c454.3 Fermi-LAT 1 year all-sky map

  5. What makes Diffuse g-rays? InterStellarMedium InterStellarRadiation Field • Diffuse Gamma-rays = Cosmic-rays x (ISM, ISRF) Galactic plane nearby gas in high latitude Planck microwave map = ISM gas

  6. Gamma-ray Sky phys. processes are well understood • GeV gamma-ray sky ~ Diffuse Gamma-rays = CRs x (ISM, ISRF) Fermi-LAT 1 year all-sky map

  7. Why are they important? • Diffuse Gamma-rays are • “probe” to study Galactic CRs and ISM • “foreground” to study exotic physics, e.g., • signal from dark matter (DM) • extragalactic g-ray background (EGB) annihilation or decay new source classes or DM signal Fermi-LAT 1 year all-sky map

  8. Example: GeV Excess (EGRET Era) • EGRET (1991-2000) reported excess emission when compared with a standard diffuse g-ray model • variety of explanations including DM signal E2 x Flux G ~ 2.7 (CR protons) excess 0.1 1 10 GeV Hunter+97

  9. Example: GeV Excess (Fermi Era) • EGRET GeV excess not confirmed. • However, Fermi data allow us investigating more subtle “anomalies” (and detailed study of CRs/ISM) E2 x Flux EGRET Fermi-LAT Abdo+09 PRL 103, 251101 G ~ 2.7 0.1 1 10 GeV

  10. Fermi-LAT as Electron Detector • Fermi-LAT reported a harder CR e- + e+ spectrum compared with a conventional model highest statistics: 4.5 M events (6 months) E3 x Flux Fermi Data (2009) Abdo+09 PRL 102, 181101 10 100 1000 GeV

  11. Fermi-LAT as Electron Detector • Fermi-LAT reported a harder CR e- + e+ spectrum compared with a conventional model • Lots of interpretations (astrophysical and exotic) Fermi e- + e+ PAMELA e+ ratio + = DM? Nearby objects?

  12. Fermi-LAT as Electron Detector • Fermi-LAT reported a harder CR e- + e+ spectrum compared with a conventional model • Lots of interpretations (astrophysical and exotic) … and the paper is highly cited 2009 Jan. – 2010 Sep.

  13. Fermi-LAT Instruments

  14. Fermi Launch • Launched on June 11, 2008 • Science Operation on Aug 4, 2008 • Orbit: 565 km, 26.5o (low BG) 5-yr mission (10-yr goal) Fermi=LAT+GBM Cape Canaveral Air Station @ Florida

  15. Fermi-LAT Collaboration France Italy Japan Sweden US • Hiroshima Univ. • Tokyo Tech • ISAS/JAXA • Waseda Univ. • Tokyo Univ. • Nagoya Univ. • Aoyama Gakuin Univ. ~400 members

  16. Large Area Telescope • Pair-conversion type g-ray telescope 20 MeV- 300 GeV • Tracker: Si-strip detectors • direction measurement ~200 um pitch => high precision tracking • ACD: plastic scintillators • BG rejection segmented tiles => prevent self-veto • Calorimeter: CsI scintillators • Energy measurement hodoscopic crystals => shower profile

  17. Large Area Telescope • Pair-conversion type g-ray telescope • Tracker: Si-strip detectors • direction measurement • Key-element of LAT, developed by HPK and Hiroshima Univ. • Low-noise (~2.5nA/cm2) • High-quality (dead strip: <0.01%) • ~106 channels in total SSD

  18. Performance of the LAT • Large FOV (2.4 sr) • Large Aeff (>=8000 cm2 in 1-100 GeV) • Good PSF (0.6 deg@ 1GeV) sensitivity to point sources EGRET 3rd Catalog 271 sources Fermi-LAT 1st year catalog 1451 sources Atwood+09

  19. Science Breakthroughs of 2009 • Fermi is recognized as one of the top science breakthroughs Science, December 2009 Discovery of 16 new pulsars

  20. GeV Gamma-ray Sky by LAT • and provides us with high-quality data! • g-ray sources, diffuse g-rays and more >100 publications as of Feb. 2011 Fermi-LAT 1 year all-sky map

  21. Diffuse g-rays as probe of CRs and ISM

  22. GeV “Non” Excess • Fermi does not confirm EGRET GeV excess local (<= 1 kpc from the sun) Diffuse Gamma-rays E2 x Flux EGRET Fermi-LAT Abdo+09, PRL 103, 251101 (CA: Johannesson, Porter, Strong) 0.1 1 10 GeV

  23. GeV “Non” Excess • Fermi does not confirm EGRET GeV excess Instead, data is compatible with a standard model Gamma = CR x (ISM, ISRF) E2 x Flux EGRET Fermi-LAT G ~ 2.7 Abdo+09 (CA: Johannesson, Porter, Strong) 0.1 1 10 GeV

  24. Diffuse gs in the Outer Galaxy • Any unexpected in diffuse gs? • Yes. New information on CRs and ISM The outer Galaxy (from outside) sun L=90deg L=270deg II quad III quad L=180deg

  25. Diffuse gs in the Outer Galaxy • Any unexpected in diffuse gs? • Yes. New information on CRs and ISM The outer Galaxy (from the Fermi-LAT) Abdo+10, ApJ 710, 133 Ackermann+11, ApJ 726, 81 GC anticenter

  26. ISM not visible by Standard Tracers • Fermi revealed ISM gas not traced by radio surveys Residual when fitted by N(HI)+CO excess gammas = residual gas Ackermann+11, ApJ 726, 81 (CA: Grenier, Mizuno, Tibaldo)

  27. ISM not visible by Standard Tracers • Fermi revealed ISM gas not traced by radio surveys • confirming an earlier claim based on EGRET study (Grenier+05) Residual when fitted by N(HI)+CO Residual gas inferred by dust Ackermann+11, ApJ 726, 81 (CA: Grenier, Mizuno, Tibaldo)

  28. More CRs than Expected • Fermi detected more gs (more CRs) than a prediction based on SNR distribution and standard CR halo Gamma-ray intensity Sun Ackermann+11 ApJ 726, 81 (CA: Grenier, Mizuno, Tibaldo) Distance from GC (kpc)

  29. More CRs than Expected • Fermi detected more gs (more CRs) than a prediction based on SNR distribution and standard CR halo • More CR sources or larger CR halo Gamma-ray intensity Sun Ackermann+11 ApJ 726, 81 (CA: Grenier, Mizuno, Tibaldo) Distance from GC (kpc)

  30. Remarks on Diffuse gs • g-rays = CR x (ISM, ISRF) • “dark gas” is confirmed (more ISM gas) • More CRs than expected in outer Galaxy • Improvement of diffuse g-ray model Basis to search for anomalies (in spectral and spatial distribution)

  31. Behind Diffuse g-rays: Study of EGB and DM search

  32. Extragalactic Gamma-ray Background • “Cosmic” Extragalactic Gamma-ray Background (EGB) has been known since 1970s G ~ 2.1 E2 x Flux CXB (resolved into AGNs) GeV background (EGRET) Sreekumar+98 keVMeVGeV

  33. Why is EGB Important? • The EGB may encrypt the signature of the most powerful processes in astrophysics Star forming galaxies Point sources or diffuse 73% Dark Energy 4% Atoms 23%Dark Matter Blazars contribute 20-100% of the EGB Annihilation of Cosmological Dark Matter Particles accelerated in Intergalactic shocks Markevitch+05

  34. The Fermi EGB LAT sky • Fermi data + improved diffuse model • new EGB spectrum in 0.2-100 GeV • carefully examine systematic uncertainty = gal. diffuse Single PL, softer than EGRET result + point sources G ~ 2.4 + Instrumental BG Abdo+10, PRL 104, 101101  0.1 1 GeV 10 100 (CA: Ackermann, Porter, Sellerholm) +”EGB”

  35. Blazar Contribution • Blazars account fora minimum of 16+-2% • Even if we extrapolate and integrate logN-logS to zero, contribution is still <40% logN-logS: Most of un-associated sources are likely to be blazars Fermi EGB vs. source contribution flatter in F<=6x10-8 0.1 1 GeV 10 100 Abdo+10, ApJ 720, 435 (CA: Ajello, Tramacere)

  36. Blazar Contribution • Blazars account for a maximum of 40% of EGB • g-ray “Fog” by Mysterious Dragons • star-forming galaxies, normal AGNs or truly diffuse? Fermi EGB vs. source contribution 0.1 1 GeV 10 100 Abdo+10, ApJ 720, 435 (CA: Ajello, Tramacere)

  37. Limits on DM Annihilation • Limits on DM by imposing the EGB is not violated 1.2 TeVm+m- 1.2x10-23 cm3/s 180 GeVgg 2.5x10-26 cm3/s 200 GeV bb 5x10-25 cm3/s 0.1 1 10 100 GeV Abdo+10, JCAP 4, 14 (CA: Conrad, Gustafsson, Sellerholm, Zaharijas)

  38. Limits on DM Annihilation • Limits on DM by imposing the EGB is not violated w/o astrophysical sources m+/m- w/ astrophysical sources 10-22 <sv> (cm3/s) Fermi PAMELA 10-25 • 1000GeV • WIMP mass Abdo+10, JCAP 4, 14 (CA: Conrad, Gustafsson, Sellerholm, Zaharijas)

  39. Limits on DM Annihilation • Limits on DM by imposing the EGB is not violated • already excluded some models, e.g., m+/m- channel favored by PAMELA/Fermi e-/e+ w/o astrophysical sources m+/m- w/ astrophysical sources 10-22 <sv> (cm3/s) Fermi fit 10-25 • 1000GeV • WIMP mass Abdo+10, JCAP 4, 14 (CA: Conrad, Gustafsson, Sellerholm, Zaharijas)

  40. Other Constraints on DM • Dwarf Spheroidal Galaxies are DM dominated • small BG (gas, star-forming activity) No detection give constraints on some models, particularly m+/m- channel m+/m- UL with CMB IC dwarfs Diffusion coeff. dwarfs Abdo+10, ApJ 712, 147 (CA: Cohen-Tanugi, Farnier, Nuss, Profumo, Jeltema)

  41. Remarks on EGB and DM search • “New” EGB spectrum in 0.2-100 GeV • Blazars account for <40% of EGB • room for star-forming galaxies, normal AGNs or truly diffuse • No evidence for DM annihilation • Constraints on models, in particular m+/m- channel • Astrophysical source contribution is important

  42. Cosmic-Ray Electrons

  43. PAMELA Positron Excess • Convincing evidence of e+ ratio excess in >10 GeV • 2ndary e+ should be softer than primary e- Sources of “Primary” e+ are required Adriani+08 0.1 1 GeV 10 100

  44. CRE by Fermi-LAT (2009) • Fermi-LAT reported hard e- + e+ spectrum • Standard models with proper choice of params are able to reproduce Fermi data alone, but not Fermi + PAMELA 6 months data 4.5 M events Abod+09 PRL 102, 181101 (CA: Latronico, Moiseev) Fermi Data (2009) 10 100 1000 GeV

  45. e-/e+ probe nearby sources • CR e-/e+ loose energy via synchrotron and IC, hence probe nearby sources We are here Our Galaxy e+ sources KEK 井岡氏の トラぺより借用

  46. CRE by Fermi-LAT (2010) • CREs collected for 12 month (data is doubled) • Cross-check with events with long path in CAL (>=13X0) • LE extention using high latitude (low cutoff) data • Noticeable deviation from a single PL 20 GeV Fermi Data (2010) pre-Fermi model Ackermann+10 PRD 82, 092004 (CA: Moiseev, Sgro) 1 10 100 GeV 1000

  47. CRE by Fermi-LAT (2010) • Noticeable deviation from a single PL • Additional e-/e+ sources (astrophysical or extocis) can provide a good fit to Fermi CRE and PAMELA e+/(e- + e+) Anisotropy of arrival direction may reveal sources or give constraints Example of an additional component Ackermann+10 PRD 82, 092004 (CA: Moiseev, Sgro) 1 10 100 GeV 1000

  48. CRE Anisotropy No-anisotropy map • Construct no anisotropy map from flight data • shuffling and direct integration • Compare obtained map with data • search for anisotoropy Eth: 60-480 GeV Angular scale: 10-90 deg Flight data sky map No evidence of anisotropy in energies/angles investigated Significance map Ackermann+10 PRD 82, 092003 (CA: Mazziotta, Vasileiou)

  49. Limit on Sources • No evidence of anisotropies • Upper limit for the dipole anisotropy: 0.5-5% • Limit already comparable to the value expected for a single nearby source dominating HE spectrum • will improve as more data are collected Dipole Anisotropy CRE spectrum at Earth Fermi (3s UL) Fermi HESS Monogem Vela Vela Monogem Ackermann+10 PRD 82, 092003 (CA: Mazziotta, Vasileiou)

  50. Summary • Diffuse g-ray emission is a powerful probe for studying CRs and ISM • Constraints on some DM models. Study of diffuse g-rays and g-ray object is important • UL of CR anisotropy is close to what is expected for single nearby source Thank you for your Attention

More Related